We have been testing the F5100 flash array in our humble lab (borrowed that term from a colleague, he knows who he is). There are two ways to use it, one is to place your datafiles on it, the other is to use it as the database flash cache.
The database flash cache feature came with 11.2 and is a way to extend the SGA. It is not the same thing as the flash cache in Exadata, read Kevin Closson's this post to find out what the difference is. F5100 is one of the products you can use as the flash cache, the other is the F20 card.
It is possible and (may be the best option) to use ASM to configure the flash cache. The documentation states that you can use a filename or an ASM diskgroup name for db_flash_cache_file parameter which is the parameter to enable the flash cache feature.
So, how do we do this?
The first step is creating an ASM diskgroup on the flash devices. In my test, for simplicity I use one flash device which is /dev/rdsk/c1t9d0s0. This is just one flash module (of size 24GB) from F5100. The process for creating the diskgroup is no different than creating a diskgroup on conventional disks, just make sure your asm_diskstring includes the flash device path. By using asmca I created a diskgroup named FLASH using external redundancy on this single flash device.
Then following the documentation I set the parameters to enable the flash cache.
SQL> alter system set db_flash_cache_size=20G scope=spfile;
A problem and a lesson